Open AccessImpact of chemically enhanced diffusion on dissolved inorganic carbon stable isotopes in a fertilized lake
Author(s) -
Bade Darren L.,
Cole Jonathan J.
Publication year - 2006
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004jc002684
Subject(s) - isotopes of carbon , dissolved organic carbon , diffusion , carbon fibers , isotope , stable isotope ratio , mass transfer , analytical chemistry (journal) , fractionation , mass transfer coefficient , chemistry , flux (metallurgy) , environmental chemistry , materials science , total organic carbon , thermodynamics , chromatography , physics , organic chemistry , quantum mechanics , composite number , composite material
At high pH the chemical reaction of CO 2 with OH − can significantly increase the mass transfer of CO 2 between air and water. The reaction of CO 2 with OH − strongly fractionates carbon isotopes in comparison to simple diffusion. These processes, chemically enhanced diffusion (CED) and chemically enhanced fractionation (CEF), greatly influence the carbon budgets and carbon isotope ratios for water bodies with high pH. Using floating chambers, we estimated mass transfer coefficients for CO 2 and a nonreactive gas, CH 4 , in an experimentally eutrophied lake. The mass transfer coefficient estimated from CH 4 flux did not vary greatly between measurements ( k 600 = 1.83 ± 0.33 cm h −1 ; mean ±1 SD) and agreed well with other independent estimates of mass transfer. The mass transfer coefficient of CO 2 , however, was chemically enhanced by 3.5‐ to 7.5‐fold. This enhancement was related to pH and temperature but was slightly higher than predictions from an existing model. We determined the role of CEF by modifying a model of CED to include both carbon isotopes ( 12 C and 13 C). A whole‐lake addition of inorganic 13 C to Peter Lake created dynamics in δ 13 C‐dissolved inorganic carbon (DIC) and provided a test of the new model. The value of δ 13 C‐DIC decreased from approximately −9‰ to −21‰, a result that was well predicted by the model including CEF but could not be duplicated when CEF was omitted. Thus CED and CEF influenced the mass balance of air‐water CO 2 exchange and had isotopic consequences for DIC. Although CEF is considered inconsequential for mean oceanic conditions, this model could be applied to marine systems for inorganic carbon modeling in areas where pH is elevated or physical mass transfer is limited because of low turbulence.